MONTEZUMA, Iowa — Maybe the seeds of rebellion are planted here along with the corn, the soybeans, the oats, rye and wheat.

Must be, because rebellion is sprouting here in a state sometimes regarded as a peaceable kingdom. It is evident in candidate appearances, in political conversations, in places where the term “prairie fire” can be a fear, not a metaphor. Throughout the summer, there has been a storm of support here for Donald Trump, the unlikely (because billionaires seldom challenge the cultural and economic system that made them rich) but ultimate (because no one else has an idiom of insurrection remotely like his) rebel.

Mr. Trump leads the Republican field here with nearly a quarter of the support of Iowans likely to participate in February’s Republican caucuses, the first major test of the political calendar. His 23 percent in the Des Moines Register/Bloomberg Poll is a stunning figure in a survey where a dozen of his competitors have numbers in single digits and three of them, whose careers together account for seven statewide election triumphs in highly competitive places, registering levels of support too small to measure.

This startling figure tells the story of the struggle for supremacy in Iowa — and in the country: A full 91 percent of Iowans say they are “unsatisfied” or “mad as hell” with politicians.

“Iowans are friendly and hospitable and also very stubborn and tough,” Republican Gov. Terry Branstad told me as he drove to a celebration honoring former University of Iowa football coach Hayden Fry, admired as much for putting a pro-farmer decal on his players’ helmets during the 1985 farm crisis as for his 143-89-6 record and his three Big Ten championships. “They’re not happy with the direction of this country. We have a huge national debt, our allies don’t trust us and our adversaries don’t fear us. That’s why a lot of the non-traditional candidates are doing so well.”

Iowans are not two-faced — they are famous for their forthrightness — but nonetheless their outlook has two faces.

On the surface the state looks like a hotbed of social rest, with a peculiar mania for both corn (it’s the country’s largest producer) and high-school wrestling (some 285 high schools have teams, including Clarksville High, which has a total enrollment of 72 students). Throughout the 1920s, Wallaces’ Farmer magazine carried an ad proclaiming that “farm women [must] learn about Jell-O like city women.”

Iowa is the state where “The Music Man” played, where Mamie Eisenhower was born, Maytag cheese was developed, Grant Wood painted and where towns hold Old Settlers celebrations that feature truck pulls, talent shows, chainsaw woodcarving and, in the town of Maxwell (population 920), which has held these events since 1901, Sunday morning chuck wagon breakfasts. The state has 39 quilting clubs; the Sioux Prairie Quilters Guild meets the first Monday of every month in the Covenant Christian Reformed Church.

But Iowa also is governed by agricultural cycles. The state still is marked by a grasshopper plague nearly a century and a half ago — “Grasshoppers came down Thursday and Friday last,” a Lyon County newspaper reported in 1873, “like snowflakes, and still cover the earth” — that prompted farmers to switch from wheat to corn.

These cycles have bred privation — and rebellion.

Where once the rebels were Democrats — they helped end Iowa's GOP domination when they repudiated native son Hebert Hoover in the 1932 election that elected Franklin Roosevelt — the insurrectionists recently have been Republicans, moving far from the moderation of the revered Gov. Bob Ray, who served from 1969 to 1983.

This began only five years after Mr. Ray left office, as Republican rebels gave television evangelist Pat Robertson second place in the caucuses. In 1996, commentator Patrick Buchanan, who deftly employed “pitchfork” rhetoric, placed within 2,866 votes of Sen. Bob Dole of Kansas, the prohibitive favorite by virtue of his agrarian-state roots and personal heritage as the war-hero son of an man who operated an egg-and-cream station. And in 2008 and 2012, religious conservatives — former Gov. Mike Huckabee of Arkansas and former Sen. Rick Santorum of Pennsylvania, respectively — actually won the caucuses.

The strong showing of Mr. Trump must be viewed in that context — and in the context of the serial rebellions that have raged across the 56,272 square miles of Iowa smudged between the Mississippi and the Missouri rivers.

Iowans have fought each other, the state’s banks, the state’s politicians. They have waged farm strikes, a cow war, even an oleo war, a bitter struggle that dated to 1880 and that resulted in legislation to ban labels on oleomargarine that suggested “any connection … with a cow, dairy or creamery.”

They have held back their crops. They have dragged a judge from his chambers and removed his trousers. They have fought over crop prices and farm foreclosures, forming vigilante groups in 1932 and pressuring Judge Miles Newberry to foreswear more foreclosures that year because, as he said, “It is simply breeding rebellion to permit actions in foreclosures to proceed.”

And they have been, in the words of Henry Wallace — magazine editor, pioneer of corn-hog ratio charts, twice a cabinet secretary, vice president and rebel 1948 Progressive Party presidential candidate — warriors “in the bitter struggle … to bring about mass action of farmers as a class that will put agriculture on a level with other occupations.” That struggle reached to 1986, when 26 Iowa banks failed, layoffs occurred at farm-implement plants and a mounted posse rounded up a Charlton-area farmer’s cattle.

The violent cow war grew out of Depression-era agrarian distress and a requirement that cattle be tested for bovine tuberculosis. Gov. Dan Turner called out the National Guard to suppress the rebellion and farmers responded by blocking 10 routes to Sioux City and emptying their milk cans into the streets.

“It was open rebellion here,” George Mills, who covered the issue for the Marshalltown Times Republican, told me before he died.

That sense of rebellion remains on display in the form of voter support for Mr. Trump and for retired surgeon Ben Carson, now in second place.

“People everywhere are somewhat frustrated,” says Bruce Nesmith, a political scientist at Coe College in Cedar Rapids. “Things aren’t going well. For a while we had a recession and that was the explanation. But now there isn’t a recession and people here still feel that things aren’t going well.”

David Shribman, a Pulitzer Prize winner in journalism, is executive editor of the Pittsburgh Post-Gazette.